1. Field of the Invention
The present invention relates to a temperature detection circuit, and in particular to a temperature detection circuit connected to a temperature sensor having a resistance varying in accordance with a temperature of a switching element.
2. Description of the Background Art
Conventionally, Intelligent Power Modules (hereinafter referred to as IPMs) having therein a switching element such as an Insulated Gate Bipolar Transistor (hereinafter referred to as an IGBT) and a control circuit for the switching element have been developed.
The IPM is also provided with a temperature sensor and a temperature detection circuit for preventing thermal failure of the switching element due to heat generated when current flows therethrough. The temperature sensor is provided on a chip on which the switching element is provided, and has a resistance varying with temperature. The temperature detection circuit is connected to the temperature sensor and outputs a signal indicating a temperature of the switching element. When it is detected based on the signal output from the temperature detection circuit that the temperature of the switching element reaches a predetermined upper limit, the control circuit controls voltage to be applied to a control electrode of the switching element and limits principal current, thus preventing thermal failure of the switching element.
Further, there is also a method of detecting a current value of a switching element based on a signal output from a temperature detection circuit and controlling principal current of the switching element based on the result of the detection (see for example Japanese Patent Laying-Open No. 2002-148288).
In a conventional temperature detection circuit, however, many electronic components constituting the temperature detection circuit each have characteristic variations, and the temperature sensor also has characteristic variations. This results in poor accuracy in temperature detection, and also causes variations in the accuracy of temperature detection among a plurality of IPMs.